Your Spine

The purpose of the spinal column is to protect the spinal cord by enclosing it in a protective "casing" and also to provide support for the body and head. The spinal column is capable of extreme flexiblity, which allows the body to be free to move in a number of directions. The spinal column is formed by a number of smaller bones known as vertebrae. and shock absorbing discs which separate and cushion the vertebrae.

Facet Joints:

Facet joints, or spinal joints, as they are normally referred, attach neighboring vertebrae to one another. Facet joints are similar to hinges and provide vertebrae with the ability to move in multiple directions, allowing the body to twist while still maintaining a range of motion within normal parameters. The surfaces of the facet joints are covered with cartilage that lets them slide against each other in a smooth manner. Further supporting the spine are a series of muscles, ligaments and discs.

Ligaments:

Ligaments are coarse bundles of dense white fibrous tissue which connect the vertebrae and strengthen the joints. Facet joints and ligaments help protect the spine by limiting how far the spine can bend or twist. One or more ligaments provide stability to a joint during rest and movement. Excessive movements such as hyper–extension or hyper–flexion, may be restricted by ligaments. Further, some ligaments prevent movement in certain directions.

Three of the more important ligaments in the spine are the Ligamentum Flavum, Anterior Longitudinal Ligament and the Posterior Longitudinal Ligament.

The Ligamentum Flavum: Forms a cover over the dura mater: a layer of tissue that protects the spinal cord. This ligament connects under the facet joints to create a small curtain over the posterior openings between the vertebrae.
The Anterior Longitudinal Ligament: Attaches to the front (anterior) of each vertebra. This ligament runs up and down the spine (vertical or longitudinal).
The Posterior Longitudinal Ligament: Runs up and down behind (posterior) the spine and inside the spinal canal.

Muscles:

Muscles are body tissue composed of long cells that contract when stimulated, and assist in maintaining the structure of the back, while allowing us movement. The back and abdominal muscles support the thoracic spine and the ribcage, while the buttocks support the coccyx and sacrum. These muscles help the spine by absorbing the shocks prior to causing damage to the skeletal structure of the back.

Spinal Cord:

The spinal cord begins at the brain and runs down to the level of the second lumbar vertebrae. The lumbar spinal nerves join to form the sciatic nerve. Spinal nerves branch out form the spinal cord.

Sciatic nerve:

The sciatic nerve branches off nerve roots off the lower end of the spinal cord. (The spinal cord ends in the lower back) Two branches run through the pelvis, deep into each side of the buttocks, through the hip, the backside of the upper leg down to the foot. . The sciatic nerve is the largest nerve in the human body - the diameter of a finger.

Discs:

The nucleus of the disc acts as a shock absorber, absorbing the impact of the body's daily activities and keeping the two vertebrae separated. The disc can be likened to a doughnut: whereby the annulus fibrosis is similar to the dough and the nucleus pulposis is the jelly. If one presses down on the front of the doughnut the jelly moves posteriorly or to the back. When one develops a prolapsed disc the jelly/ nucleus pulposus is forced out of the doughnut/ disc and may put pressure on the nerve located near the disc. This can give one the symptoms of sciatica.

Cervical vertebra with intervertebral discThere is one disc between each pair of vertebrae, except for the first cervical segment, the atlas. The atlas is a ring around the roughly cone-shaped extension of the axis (second cervical segment). The axis acts as a post around which the atlas can rotate, allowing the neck to swivel. There are a total of twenty-three discs in the spine, which are most commonly identified by specifying the particular vertebrae they separate. For example, the disc between the fifth and sixth cervical vertabrae is designated "C5-6".

Vertebrae:

A vertebra (plural: vertebrae) is an individual bone in the flexible column that defines vertebrate animals, e.g. humans. The vertebral column encases and protects the spinal cord, which runs from the base of the cranium down the dorsal side of the animal until reaching the pelvis. From there, vertebra continue into the tail. Vertebrae are defined by the regions of the vertebral column they occur in. Cervical vertebrae are those in the neck area. With exception of two sloth species (Choleopus and Bradypus) and the manatee (Trichechus) all mammals have seven cervical vertebrae[1]. In other vertebrates it can range from a single vertebra in amphibians, to as many as 25 in swans or 76 in the extinct plesiosaur Elasmosaurus. The dorsal vertebrae range from the bottom of the neck to the top of the pelvis. Dorsal vertebrae attached to ribs are called thoracic vertebrae, while those without ribs are called lumbar vertebrae. The sacral vertebrae are those in the pelvic region, and range from one in amphibians, to two in most birds and modern reptiles,

The 24 vertebrae:

Cervical spine (neck area) with 7 vertebrae (labeled C1 - C7)

Thoracic spine (chest area) with 12 vertebrae (labeled T1 - T12)

Lumbar spine (lower back) with 5 vertebrae (labeled L1 - L5)

Below the lumbar spine:

Sacrum:

The sacrum is a shield-shaped bony structure that is located at the base of the lumbar vertebrae and that is connected to the pelvis. The sacrum forms the posterior pelvic wall and strengthens and stabilizes the pelvis. Its upper part connects with the last lumbar vertebra, and bottom part with the coccyx (tailbone). In children, it consists of usually five unfused vertebrae which begin to fuse between ages 16-18 and are usually completely fused into a single bone by age 26. It is curved upon itself and placed obliquely (that is, tilted forward). It is kyphotic — that is, concave facing forwards. The base projects forward as the sacral promontory internally, and articulates with the last lumbar vertebra to form the prominent sacrovertebral angle. The central part is curved outward towards the posterior, allowing greater room for the pelvic cavity.

Coccyx:

The coccyx is usually formed of four rudimentary vertebrae (sometimes five or three). It articulates superiorly with the sacrum. In each of the first three segments may be traced a rudimentary body and articular and transverse processes; the last piece (sometimes the third) is a mere nodule of bone. The transverse processes is most prominent and noticeable on the first coccygeal segment. All the segments are destitute of pedicles, laminae and spinous processes. The first is the largest; it resembles the lowest sacral vertebra, and often exists as a separate piece; the last three diminish in size from above downward. The anterior surface is slightly concave and marked with three transverse grooves that indicate the junctions of the different segments. It gives attachment to the anterior sacrococcygeal ligament and the Levatores ani and supports part of the rectum.The posterior surface is convex marked by transverse grooves similar to those on the anterior surface, and presents on either side a linear row of tubercles, the rudimentary articular processes of the coccygeal vertebrae. Of these, the superior pair are large, and are called the coccygeal cornua; they project upward, and articulate with the cornua of the sacrum, and on either side complete the foramen for the transmission of the posterior division of the fifth sacral nerve.

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